A conventional locking device for a desk with a tiltable desk top has first and second segments which are telescopically connected to each other, and which can be locked to each other at a plurality of predetermined locking positions. The first segment has a first connection end which is opposite to the second segment, and which is connected to a lower surface of the desk top. The second segment has a second connection end which is opposite to the first segment, and which is connected to a desk leg. By adjusting the length of the locking device, the tilt angle of the desk top can be adjusted.